In order to discharge the fluid content of a bottle sealed up with a conventional bottle cap, it is usually necessary to first remove the cap. Besides, it is often difficult to control the discharge rate of the fluids by pouring straight from the open bottle mouth. Bottle caps have been provided with inner threads provided on the bottom, and a little hole left on top so as to refrain from removing the cap. Still, when it is intended to discharge the fluid contents, it is necessary to loosen the cap made in this manner before letting out the fluids from the little hole provided on top. The biggest drawback with such caps is that in order to hold onto the bottle body, particularly with those bottles made of plastics or materials other than ceramic glasswares, as a first step to discharge the fluid contents, a pressure, big or small, will be reflected to the bottle mouth. With the cap loosened, the inner threads on the bottom of the cap will easily get detached from the bottle mouth as a result of the pressure induced thereto and eventually result in an unwanted liberal release of the fluid contents.